Click Click Boom!!!!!

Counterbore wear is due to the engine twisting during operation and the liners flexing in the hole. 1 and 6 are stiffened up by the front and rear structures and also close to the mounting points. Thats why 2 and 5 are the most common for fretting.
We have cut a couple high milage X15s but both are lower serial numbers 79xxxxx.
Ran across 2 cracked counterbores. One we swapped the engine. The other someone else had cut over .060" deep and put it together with 3 shims stacked. It ran a year or so then the cracked counterbore split even worse and shifted vertically. We swung a motor in that one too.

 

I have heard two theories. Official is like you said the torsional twisting of block and distortion of liners when firing. Second idea floated around is block settling. Cummins used to season blocks before machining, don't anymore. Local guy that works at Cummins said engineering team said this does play into equation. I know early on we had problem of random broken bolts on rear of EGR cooler on our 871's.

 

I heard that too.
I believe the "official" reason is more of the cause as lower hp ones seemed to not be affected and high hp ones pulling super bs were alot more failure prone.
Block settling/ relaxing is true as well though.
Wasnt it rolls royce who would cast em and chuck them out in the weeds for a year before final machining?

 

I know when Cummins used to build truck engines in Columbus vs Jamestown they stored blocks outside for months before machining.

 

How did Cummins Season Blocks..Very interesting conversation...

 

Like trees. Cut down, leave aside for a year or so, then turn them into beautiful log house that will stand the test of time.

 

From what I've been told from friends that worked @ Cummins, most of the engine blocks of the old Big Cams and N-14 were cast @ Golden Foundry in Columbus, IN. It closed in early 2000's. A lot of the blocks were stored outside before machining. It is known that colder temps help reduce stress in cast iron components. I am sure this probably is done some extent in a factory settings/process. The ISX/ X series is cast by Tupy Manufacturing out of Brazil. They have foundries in Brazil and Mexico and cast for most all OEM's. They are shipped to Jamestown, NY for machining and production. It is done on the just in time manufacturing theory of today and don't sit around like they used to. I think NY would be a great climate to season components, but sure it doesn't make financial sense.

 

Are you saying I should’ve rebuilt the BXS ACERT outside in -30°c winter of Ontario, that it would’ve helped reduce stress on new cast iron components I installed?